1. Field of the Invention
The present invention relates to a method of selecting a network path and a communication system.
2. Description of the Related Art
When sending data from a source to a destination in a network that connects communication devices (hereinafter, “nodes”) and communication paths (hereinafter, “links”), each node performs a switching process of outputting input data to a desired destination in a conventional packet communication. In the packet switching process, only packet sorting into the destinations is performed, and no process is performed on user data in the packet. By contrast, a recent noticeable network coding technology has enabled each node to perform coding in addition to the switching process, so that network-wide efficient transmission is attained.
A first feature of the network coding is streamlining of transmission, i.e., effective utilization of communication resources such as band frequencies. The conventional network coding technologies for wide and effective communication to a plurality of destinations are disclosed in Japanese Patent Application Laid-open No. 2006-31693; R. Ahlswede et al., “Network Information Flow”, IEEE tran. on Information Theory, vol. 46, No. 4, July, 2000, pages 1204 to 1216; Miki Yamamoto, “Network Coding”, The Journal of the Institute of Electronics, Information, and Communication Engineers, vol. 90, No. 2, February, 2007, pages 111 to 116; S-Y. R. Li et al., “Linear Network Coding” vol. 49, No. 2, February, 2003, pages 371 to 381; T. Ho, M. Medard, R. Koetter, D. R. Karger, M. Effros, B Leong, “A Random Linear Network Coding Approach to Multicast”, IEEE Transactions, Information Theory, Vol. 52, No. 10, Pages 4413 to 4430, October, 2006.; J.-S. Park, M Gerla, D. S. Lun, Y. Yi, M. Medard, “Code-Cast: A Network-Coding-Based Ad Hoc Multicast Protocol”, IEEE Wireless Communication Vol. 13, No. 5, October, 2006, pages 76 to 81.
The conventional network coding technologies offer methods for efficiently transmitting date to a plurality of destinations; however consideration is not given to surely transmitting data to specific destinations and reducing the risk of possible interception that can be prevented by avoiding unnecessary communication. Therefore, data deliveries to designated destinations are not ensured and possibility of the interception is not reduced.
The above documents “A Random Linear Network Coding Approach to Multicast” and “Code-Cast: A Network-Coding-Based Ad Hoc Multicast Protocol” disclose technologies in which each node selects the coding methodology at random, and selects and transmits information. If the processing fails, the packet is discarded. Thus, consideration is not given to the surely transmitting of information and the avoiding of the unnecessary communication.